Sash balance



Aug. 17, 1954 Filed Jan. 12, 1951 A. M. STARCK 2,686,333

SASH BALANCE I 2 Sheets-Sheet 1 INVENTOR ATTO R N EYI) A. M. STARCK SASH BALANCE 2 Sheets-Sheet 2 Filed Jan. 12 1951 INVENTOR fi/fiurMJ/oro BY ATTORNE Patented Aug. 17, 1954 UNITED STATES ATENT OFFICE 14 Claims. 1

This invention relates to improvements in window sash balances, and more particularly balances for windows of the sliding sash type wherein the sashes, mounted for vertical movement, are counterbalanced by elongated coil springs.

Heretofore when coil springs have been used to balance window sashes, the balancing action has resulted either from stretching the spring, or from turning the spring.

Balancing action through stretching a coil spring can be accomplished merely by attaching one end of the coil spring to the sash and attaching the other end of the coil spring to the window frame at a point above the connection to the sash. This method of balancing a window sash is subject to the objection that the balancing efi'ect varies greatly as the sash is raised or lowered. This is true, because as the spring is stretched progressively more and more, the spring tension increases, while the weight of the sash remains constant.

Balancing action through turning a coil spring usually is accomplished by attaching one end of the coil spring to the window frame so that it cannot turn, and by causing the free end of the spring to turn as the sash is raised or lowered. The spring may be caused to turn by means of a spiral rod which is secured at one end to the sash and which slidably engages a slot in a bushing secured on the free end of the spring. If the pitch of the spiral rod is uniform, the erlective balancing effort of the spring varies as the spring is wound tighter, or unwound, by turning the end of the spring and will vary widely from one end of the sash run to the other end. The Larson patent No. 1,864,745, June 28, 1932 discloses a balance of this general type wherein the spiral rod secured to the window sash is given an accelerated pitch, so as to provide a more nearly uniform balancing eifect for all positions of the sash in its run.

According to the present invention a window sash balance is provided in which the balancing action is attained by both stretching and turning an elongated coil spring, and in which a more nearly uniform balancing eiiect can be attained for all positions of the sash in its run. The balancing effect produced by stretching the spring is reinforced by the balancing effect resulting from turning the spring in the first part of the downward movement of the sash. As the sash moves downwardly the rate at which the spring is being turned decreases, and then reverses, so that toward the lower end of the sash run the balancing effect from turning the spring is decreasing to compensate for the increased spring tension.

The present invention will be illustrated and described as an improvement in a combined parting bead and dual sash balance such as is disclosed in my copending patent application, Serial No. 112,264, filed August 25, 1949 and patented February 17, 1953, No. 2,628,390. While the present improvements are peculiarly adapted for embodim'ent in the arrangement disclosed in my earlier application, it will become evident as the following description proceeds, and it will appear from the appended claims, that features of the invention herein disclosed are not limited in their use to the combined parting bead and dual sash balance housing of my aforesaid application, but have utility in other constructions.

It is an object of the present invention to provide improved window sash balances. It is an object of the invention to provide improved sash balances of the type in which the balancing is efiected by means of an elongated coil spring. A further object of the invention is to provide a spring type sash balance in which it is possible for a substantially uniform balancing effect to be exerted for all positions of the sash in its run. Another object, of the invention is to provide a sash balance which may be easily adjusted at the time of installation to permit its use for balancing sashes of difierent weights. Still another object of the invention is to provide a sash balance in which the balancing effect is exerted by a combined stretching and turning of the coil spring as the sash is moved in its run. It also is an object of this invention to provide improved means for connecting coil spring sash balances to window sashes. Further objects and advantages of the invention will appear hereinafter as the descrip tion proceeds,

A preferred embodiment of the invention se-v lected for purposes of illustration and description is shown in the accompanying drawings, in which:

Figure 1 is a perspective view showing a combined parting bead and dual sash balance for a double hung window, fragmentary portions of the window frame and sashes being indicated to disclose the relation of the parts;

Figure 2 is a side elevation of the spiral rod employed for turning the'coil spring;

Figure 3 is a vertical section through the sash balance structure shown in Figure 1, this view being greatly shortened merely for convenience of illustration;

Figure 4 is a transverse sectional view through the sash balance structure of Figure 1, substantially looking down on the top of the S-shaped member;

Figure 5 is a perspective view, to enlarged scale as compared to Figure 1, of means for connecting the sash balance to the upper sash; and

Figure 6 is a perspective view, also to enlarged scale as compared to Figure 1, of means for connecting the sash balance to the lower sash.

Referring first to Figure 1 of the application drawings, H represents one side jamb of a Window frame for double hung sashes, l2 represents the inner bead, and l 3 the outer bea'd. The upper sa h is indicated, in fully raised position, at 4, and the lower sash, partially raised, at l5. The construction thus far is conventional and further description thereof is believed unnecessary.

In double hung windows wherein the sashes are balanced by means of coil spring balances it is the usual practice to separate the side edges of the two sashes with solid parting bead and to employ individual spring balances for each side of each sash, these sash balances being recessed either in the side edges of the sashes, or in the side jambs of the window frame. In the illustrative embodiment of Figure 1, the side edges of the upper and lower sashes are separated by a combined parting bead and dual sash balance designated generally at Hi, the construction being similar, except for the sash balance of the present invention, to that disclosed in my aforementioned co-pending patent application. It will be obvious from the following description that certain features of the present invention may be embodied in individual sash balances which are to be recessed in the side edges of the sashes, or in the side jambs of the window frame.

Accordingto the present invention, the coil spring sash balances are enclosed and concealed within elongated housings which are to be attached to the side jambs of the Window frames. In a double hung window, both sash balances desirably are enclosed within a housing which replaces the conventional parting head, as shown in Figure 1 of the application drawings.

In the illustrative embodiment of Figure 1, the

combined parting bead and dual sash balance housing comprises an elongated channel-shaped upper member El, and aligned therewith an elongated S-shaped lower member is. The s-shapcd housing member it has relatively narrow openings 22 and 23 extending longitudinally thereof and provides two parallel tubular chambers with these narrow openings therefrom facing in opposite directions. The housing members El and I8 ordinarily will be made of sheet metal, for example aluminum, and may be formed into shape in suitable manner, as by rolling.

In the illustrative embodiment, the upper housing member i! is rectangular in shape and the edges of the metal strip from which the channel is made preferably extend in overlappingre lation on one of the narrow sides or edges of the member. Preferably the balance housing memher I 7 has the same dimensions as the solid wood parting bead which it replaces so that one edge thereof can be pressed into the groove in the side janib I i, just as would the solid parting bead, and without the necessity of any change in the construction of the window frame. Ordinarily the edge of the member I! tobe pressed into the groove in the'side jamb will be the one having the overlapping edges of the metal strip from which the member i! is formed.

Located within the channel-shaped housing member ll are two parallel coil springs i9 and 20, somewhat shorter than the housing member H. These are the springs for balancing the upper and lower sashes, respectively. A fitting 2! which is slidable in the upper portion of the channel-shaped housing member H is secured to the upper ends of the coil springs i9 and 2G and prevents rotation thereof. When the sash balance is installed in a window frame the fitting 2| will be secured by the workman against movemerit within the chainiel-shaped housing member H. The position at which the fitting 2i is secured within the channel-shaped housing member ll will determine the tension on the coil springs 52 and 20, and the higher the location of the fitting 21, the greater the spring tensions, and the greater the counterbalanclng effect on the window sashes.

Advantage may be taken of this fact to adjust the spring tension at the time of installation to accommodate for the weight of the particular window sash with which the balance is to be used. This is advantageous because it permits the use of one size of balance with sashes of different weights, thus reducing the number of sizes of sash balances which must be manufactured and stocked.

For the purpose of securing the fitting 2! against movement within the channel-shaped housing member ll, the fitting may be provided with a hole 24 to receive a pin, for example a nail or screw 25, which extends through aligned holes in opposite narrow walls of the channelshaped housing member H and into the side jamb i i of the window frame. Not only does this nail or screw secure the fitting 2% against movement within the channel-shaped housing member, but it aifixes the channel-shaped housing member to the side jamb.

For making the initial tension adjustment on the coil springs l9 and 20, the walls of the channel-shaped housing member ll desirably are provided with a series of holes 26. The sash balance may be calibrated so that by matching the hole 24 in the fitting 2| with the proper holes 26 through the walls of the channel-shaped housing member, the desired spring tension can be obtained. For example, in one particular sash balance which has been made by applicant and in which the coil springs are about l8 inches long, there need be little or no initial stretching of the springs for balancing a sash weighing up to about 1 /2 pounds, whereas the springs should be stretched initially about 2% inches for a sash weighing 6 pounds, about 5 inches for a sash weighing 9 pounds, and about 7 inches for a sash weighing 12 pounds. Thus it is seen that a single sash balance made according to the present invention can be used efficiently with sashes of widely differing weights.

According to this invention, means are provided for stretching the springs i9 and 28 within the channel-shaped housing member i! by a simple operation to make the initial adjustment of tension in the springs at the time of installation. This is accomplished by means of a band 21, for example a wire, attached at one end to the fitting 2i and at its other end to a take-up axle 2B in the upper end of the channel-shaped housing member H.

In the illustrative embodiment the take-up comprises an axle rotatably mounted in slots in the upper end of the channel-shaped housing member ii. This take-up axle 28 is mounted in horizontal position in the longer transverse axis of the channel-shaped housing member. The length of the take-up axle preferably is the same as, or very slightly greater than, the longer transverse axis of the channel-shaped housing member. The take-up axle is provided near its end with collars 3? which engage the walls of the channel-shaped housing member. These collars hold the axle against movement longitudinally, but do not interfere with rotation of the axle. One end of the band 21 is secured to the axle 28.

The end of the take-up axle which will be exposed when the channel-shaped housing member H has been pressed into the groove of the side jamb of the window casing is slotted, as shown at 29, to receive the end of a screw driver. Thus it will be apparent that after the combined parting bead and sash balance has been inserted in its groove in the window frame, the take-up axle 28 can be turned, simply by using a screw driver, to lift the fitting 25 until the hole 24 therethrough matches the proper holes 25 in the walls of the channel-shaped housing member for counterbalancing the weight of the sash, and the nail or screw 25 can then be driven home to hold the fitting 2! against further movement within the housing member [1, and also to secure the parting bead and sash balance to the window frame.

Secured on the lower end of each of the coil springs ii and 2b is a bushing which is slotted to receive slidably a spiral rod, these bushings being designated 3t and 3|, respectively. In the illustrative embodiment the spiral rods are elongated metal strips which have been twisted about their longitudinal axes. Also secured to the lower ends of the coil springs are connecting links extending laterally outwardly through the narrow longitudinal openings in the S-shaped housing member, these connecting links being designated and 33. Each connecting link is secured to its spring in such a manner as to permit turning of the end of the spring as the link and the end of the spring to which it is connected are moved up or down within the S-shaped housing member l8. Conveniently this connection is made by having the inner end of the link bent around the bushing and lying in a circumferential groove therein, as is disclosed in Figures 3 and. i of the application drawings, so that the bushing is free to turn with respect to the connecting link.

The link 32 associated with the upper sash balancing spring is is connected to the upper sash is at or near its lower edge, and the link 33 associated with the lower sash balancing spring 2 is connected to the lower sash I5 at or near its lower edge.

In fitting a window sash in a frame it is customary to leave a certain amount of play to prevent binding of the sash in the slides as the sash is raised or lowered. Subsequent shrinkage of the wood may increase the amount of play. For these reasons the connections between the links 32 and 33 and the sashes should permit slight movement of the sashes horizontally, mainly in the planes of the sashes, without binding connecting links against the walls of the s-shaped member l8, or elsewhere on the window frame. Preferred means for connecting the links 32 and 33 to the sashes are shown in Figures 5 and 6.

Figure 5 shows a connection for the upper sash. As has been described, the inner end of the link 32 encircles the bushing 36 and is free to turn on the bushing within the limits imposed by the side edges of the narrow opening 22. The outer end of the link preferably is curved back on itself to form a loop, as shown. This loop portion of the link engages a socket member 42, preferably secured to the lower edge of the upper sash, as by screws. The socket fits the loop somewhat loosely so that the sash is free to move horizontally, within the window frame, without any binding of the parts. The socket member may be made of cast metal, or it may be made of sheet metal, folded substantially to the form shown.

In double hung windows the vertical dimension of the upper sash may be somewhat less than that of the lower sash. In the event that it should be desired to limit the downward movement of the upper sash this can be done easily by forming integrally with the socket member 42 a downwardly projecting arm 43. When the lower end of the arm 43 reaches the window sill, downward movement of the sash will halt.

Figure 6 shows a connection for the lower sash. As has been described, the inner end of the link 33 encircles the bushing 3! and is free to turn on the bushing within the limits imposed by the side edges of the narrow opening 23. As in the case of link 32, the outer end of link 33 is curved back on itself to form a loop, as shown. This loop portion of link 33 engages a socket member 33, preferably set in an opening in the side of the sash stile near the bottom of the sash. The socket which may be made of cast metal, or of sheet metal, fits the loop somewhat loosely, so that the sash is free to move horizontally, within the window frame, without any binding of the parts.

It will be evident from the description thus far that as the upper sash it is lowered from its closed position, the link 32 and the bushing 39 connected to the lower end of the spring i9 will be moved downwardly within the S-shaped housing member l8, and that this will stretch the spring 59. When the lower sash i5 is in closed position, its connecting link 33 will be at its lowermost position and the coil spring 253 will be at its maximum elongation. Raising the lower sash I5 will cause the link 33 and the bushing 3! connected to the lower end of the spring 28 to be moved upwardly.

Within each chamber of the S-shaped housing member i 8 is a spiral rod, spiral rod 34 being engaged by the bushing 3i) secured on the lower end of the coil spring l9, and spiral rod 35 being engaged by the bushing 31 secured on the lower end of the coil spring 24}. In length, these spiral rods ordinarily will be substantially co-extensive with the S-shaped housing member It. When installed, the spiral rods 3 and 35 are secured at their lower ends against rotation and also against movement longitudinally within the chambers of the S-shaped housing member. Desirably this is accomplished by means of a pin, for example a nail or screw 36 passing through aligned openings in the walls of the S-sha-ped housing member 58 and through holes in the lower ends of the spiral rods, into the side jamb i i, to secure the S-shaped housing member firmly in its groove in the side jamb of the Window casing.

To facilitate orienting the lower ends of the spiral rods 34, 35 within the S-shaped housing member l8 prior to inserting the nail or screw 38,

the lower ends of the rods desirably are engaged by slotted blocks or box-like members 38, 39. These may be blocks of fiber, plastic or other material, or they may be boxlike and made from sheet metal. In either case they are provided with transverse holes to receive the nail or screw 36. These members 38, 39 should not be free to turn within the chambers of the S-shaped hcusing member, and when at the bottom of the S- shaped housing member the holes through the walls of the housing member, and through the members 38 and 39, and through the lower ends of the spiral rods 34 and 35 all will be aligned to receive the nail or screw 38'.

From the foregoing it will be understood that as either window sash is moved vertically, its connecting link causes a change in the length of the associated coil spring and, by moving the bushing connected to the lower end of the spring up or down along the spiral rod, simultaneously produces a turning of the rotatable end of the coil spring.

In the present invention the combined effect of stretching and turning the coil spring is utilized to provide a controlled and more nearly uniform balancing effect for the window sash at all points in the sash run. This is accomplished, in part, by turning the end of the spring to cause the spring to be coiled tighter at a fairly rapid rate at the beginning of the spring stretching operation. This reinforces the relatively low tension resulting from stretching the spring at the beginning of the stretching operation. As the spring is stretched further by continued downward movement of the sash, the balancing efiect produced merely by stretching the spring increases, and to compensate for this the rate of turning the rotatable end of the spring will be reduced by reason of an increase in the pitch of the spiral rod which engages the slot in the bushing secured to the lower end of the spring.

However, since the length of the sash run generally will be approximately equal to the length of the coil spring, a more uniform balancing effect than can be attained merely by increasing the pitch of the spiral rod is desirable. This improvement in the uniformity of the balancing effect is attained by reversing the pitch of the spiral rod intermediate its ends, and then decreasing the reversed pitch as the -ash approaches the lower limit of travel in its run. In this way the coil spring, which has been wound tighter as the spring has been stretched, now will be unwound at a progressively increasing rate as the coil spring is stretched further toward the r."

limit of its extension. As a result, the balancing effect on the window sash resulting from the turning of the spring is reduced to compensate for the substantially greater balancing effect resulting from the stretching of the spring as it becomes longer.

In one embodiment made by applicant the coil spring was approximately 18 inches long and inches in outside diameter, in unstretched condition, and the spiral rods were approximately 26% inches long. In that embodiment the pitch of the spiral rod increased from about 1 inches at the upper end of the rod to approximately 5 inches just before reversal of the pitch at the approximate mid-point of the rod, and then decreased from approximately 4 inches in the reverse direction to about 1 inches at the lower end of the rod.

For double hung sash the balance housing preferably will be a two-part construction as illustrated. In a balance intended for a single sliding sash the balance housing which is to be attached to the side jamb of the window frame might be either a two-piece or a unitary channelshaped member enclosing both the coil sprin and the spiral rod. The channel-shaped member would be slotted longitudinally at its lower end to receive the link connecting the balance to the sash.

It will be understood that a considerable variation in the design of the spiral rod is permissible. In the illustrative embodiment shown in Figure 2 of the application drawings the pitch of the rod 41 decreases at a progressively slower rate toward both ends of the rod from the point of reversal 59 approximately at the mid-point of the rod.

In order to retain a sash firmly seated in its uppermost position, the balancing coil spring may be placed under initial tension at the time of in stallation, in the manner hereinabove described, or the rotatable end of the spring may be turned initially to tighten the coil of the spring, or there may be a combination of stretching and turning the spring to obtain the desired balancing efiect.

It will be understood that the fitting 2 I, shown in the drawings as a block, may be a box-like metal structure.

The invention herein disclosed may be variously modified and embodied within the scope of the subjoined claims.

I claim:

1. In a window structure including a frame and two sashes mounted therein for sliding movement vertically past each other, in combination, a sash balance comprising aligned, elongated, upper and lower balance housing members separating side edges of the two sashes, the upper member being channel-shaped and containing two elongated coil springs arranged side by side, a slotted bushing secured on the lower end of each coil spring, a fitting slidably contained within the upper portion of the channel-shaped member and secured to the upper ends of the coil springs to prevent rotation thereof, a band secured at one end to the slidable fitting and at its other end to a take-up in the upper end or the channel-shaped member, means for adjusting the take-up to raise the fitting in the channel-shaped member, means for securing the fitting in adjusted position within the channel-shaped member, the said lower member having similar over-all dimensions to the channel-shaped upper member and being S-shaped in transverse section with relatively narrow, longitudinally extending openings into the two tubular chambers thus formed, each such chamber containing a spiral rod which slidably engages the slot in the bushing on the lower end of one of the aforesaid coil springs to turn the end of the spring upon relative movement of the spiral rod into or out of the spring, a connecting link attached to the lower end of each coil spring and extending laterally outwardly through the narrow opening in the S-shaped member, means connecting each said link to one of the sashes, and means for securing the lower ends of the spiral rods against rotation and against movement longitudinally in the S-shaped member.

In a window structure including a frame and two sashes mounted therein for sliding movement vertically past each other, in combination, a sash balance comprising aligned, elongated, upper and lower balance housing members separating side edges of the two sashes, the upper member being channel-shaped and containing two elongated coil springs arranged side by side, a slotted bushing secured on the lower end of each coil spring, means for securing the upper ends of the coil springs against rotation and against movement longitudinally in the channel-shaped member, the said lower member having similar over-all dimensions to the channel-shaped upper member and being S-shaped in transverse section with relatively narrow, longitudinally extending openings into the two tubular chambers thus formed, each such chamber containing a spiral rod which slidably engages the slot in the bushing on the lower end of one of the aforesaid coil springs to turn the end of the spring upon relative movement of the spiral rod into or out of the spring, a connecting link attached to the lower end of each coil spring and extending laterally outwardly through the narrow opening in the S-shaped member, means connecting each said link to one of the sashes, and means for securing the lower ends of the spiral rods against rotation and against movement longitudinally in the S-shaped member.

3. A sash balance for a window having two sashes mounted for sliding movement vertically past each other, comprising, in combination. aligned upper and lower elongated members, the upper member being channel-shaped and containing two elongated coil springs arranged. side by side, a slotted bushing secured on the lower end of each coil spring, means for securing the coil springs against rotation at their upper ends to a fitting slidably mounted within the channelshaped member, means for securing the fitting against movement longitudinally within the channel, the lower member having similar overall dimensions to the channel-shaped upper member and being S-shaped in transverse section with relatively narrow, longitudinally extending openings into the two tubular chambers thus formed, each such chamber containing a spiral rod which slidably engages the slot in the bushing on the lower end of one or" the aforesaid coil springs, a connecting link attached to the lower end of each coil spring and extending laterally outwardly from the S-shaped member through the narrow opening for connection to a Window sash, and means for securing the lower ends of the spiral rods against rotation and against movement longitudinally within the S-shaped member.

4. A. sash balance according to claim 3, including, in combination, a take-up in the upper end of the channel-shaped member, a band interconnectin the take-up and the fitting within the channel-shaped member, and means for adjusting the take-up to raise the fitting and the upper ends of the coil springs prior to securing the fitting against movement within the channel-shaped member.

5. A sash balance according to claim 3, characterized by the fact that the pitch of each spiral rod increases from its upper end for a portion of the length of the rod to coil the spring tighter at a decreasing rate as the sash is lowered, and then reverses and decreases toward the lower end of the rod to uncoil the spring at an increasing rate as the lowering of the sash is continued.

6. A sash balance according to claim 3, including, in combination, a take-up in the upper end of the channel-shaped member, a band interconnecting the takeup and the fitting within the channel-shaped member, and means for adjusting the take-up to raise the fitting and the upper ends of the coil springs prior to securing the fitting against movement within the channelshaped member and characterized by the fact that the pitch of each spiral rod increases from its upper end for a portion of the length of the rod and then reverses and decreases toward the lower end of the rod.

7. In a window structure having a frame and a vertically slidable sash therein, sash balancing means for supporting the sash in adjusted position, comprising, in combination, an elongated balance housing secured to said frame and along which one of the stiles of the sash slides, said housing having a longitudinally extending slot facing the stile, an elongated coil spring within the upper part of said housing and secured at its upper end against rotation and against movement longitudinally within the housing, a slotted bushing secured on the lower end of the coil spring, a spiral rod within the lower part of the housing slidably engaging the slot in the bushing on the lower end of the coil spring to turn the end of the spring upon relative movement of the spiral rod into or out of the spring, means for securing the lower end of the spiral rod against rotation and against movement longitudinally within the housing, a connecting link attached to the lower end or" the coil spring and permitting rotation thereof, said connecting link extending outwardly through the slot in the housing, and means for connecting said link to the sash.

8. A counterbalance for a sliding window sash comprising, in combination, an elongated balance housing to be secured to a side jamb of a window frame, a longitudinally extending slot in the side of the housing which will face a stile of the window sash, an elongated coil spring with in the upper part of the housing, a slotted bushing secured on the lower end of the coil spring, a spiral rod within the lower part of the housing slidably engaging the slot in the bushing on the lower end of the coil spring to turn the end of the spring upon relative movement of the spiral rod into or out of the spring, means for securing the upper end of the coil spring against rotation and against movement longitudinally within the housing, means for securing the lower end of the spiral rod against rotation and against movement longitudinally within the housing, and a connecting link attached to the lower end of the coil spring and permitting rotation thereof, said connecting link extending outwardly through the slot in the housing for connection to a window sash.

9. A counterbalance for a sliding window sash comprising, in combination, an elongated balance housing to be secured to a side jamb of a window frame, a longitudinally extending slot in the side of the housing which will face a. stile of the window sash, an elongated coil spring within the upper part of the housing, a slotted bushing secured on the lower end of the coil spring, a spiral rod within the lower part of the housing slidably engaging the slot in the bushing on the lower end of the coil spring to turn the end of the spring upon relative movement of the spiral rod into or out of the spring, a fitting secured to the upper end of the coil spring, matching openings in the upper part of the wall of the housing and in the fitting secured to the upper end of the coil spring to receive a pin for locking the upper end of the coil spring against rotation and against movement longitudinally within the housing, matching openings in the lower portion of the wall of the 11 housing and in the lower end of the spiral rod to receive a pin for locking the lower end of the spiral rod against rotation and against movement longitudinally within the housing, and a connecting link attached to the lower end of the coil spring and permitting rotation thereof, said connecting link extending outwardly through the slot in the housing for connection to a. window sash.

10. A counterbalance for a window sash according to claim 9, characterized by the fact that the elongated balance housing comprises aligned, elongated upper and lower members, that the coil spring is within the upper member, that the spiral rod is within the lower member, and that the lower member has a narrow, longitudinally extending opening comprising the slot through which the connecting link attached to the lower end of the coil spring projects.

11. A counterbalance for a window sash according to claim 9, including, in combination, a takeup in the upper end of the balance housing, a band interconnecting the take-up and the fitting secured to the upper end of the coil spring, and means for adjusting the take-up to raise the upper end of the coil spring prior to inserting a pin for locking the upper end of the coil spring within the housing, characterized by the fact that there are a plurality of openings spaced longitudinally in the upper part of the housing wall through which a pin may be inserted into the fitting secured to the upper end of the spring.

12. A counterbalance for a window sash according to claim 9, characterized by the fact that the pitch of the spiral rod increases from its upper end for a portion of the length of the rod to coil the spring tighter at a decreasing rate as the sash is lowered, and then reverses and decreases toward the lower end of the rod to uncoil the spring aesasss 12 at an-increasing rate as the lowering of the sash is continued.

13. A coil spring sash balance comprising, in combination, an elongated balance housing, an elongated coil spring within the upper part of the balance housing, a bushing secured to the lower end of the spring, a spiral rod within the lower part of the balance housing slidably engaging the bushing to turn the end of the spring upon relative movement of the spiral rod into or out of the spring, means for locking the upper end of the coil spring against rotation and against movement longitudinally within the balance housing, means for locking the lower end of the spiral rod against rotation and against movement longitudinally within the balance housing, a longitudinally extending slot in the lower part of the housing, and a connecting link attached to the bushing on the lower end of the coil spring and extending outwardly through the slot in the balance housing for connection to a window sash, the bushing having a circumferential groove to receive the connecting link and being rotatable relative thereto.

14. A coil spring sash balance according to claim 13, characterized by the fact that the connecting link is a metal strip, the inner end of which substantially encircles the bushings in its circumferential groove, and the outer end of which is curved back on itself to form a loop.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,383,982 Chaffee July 5, 1921 2,306,193 Stepan Dec. 22, 1942 2,477,069 Larson July 26, 1949 2,565,804 De Vries et a1 Aug. 28, 1951 

